Studies involving the evaluation of protein quality by in vitro enzymatic digestion techniques continue. A dynamic digestion cell, consisting of a hollow fiber osmolyzer was found inadequate for this purpose because of the low transfer rate for free amino acids (less than 17%/h). Further evaluation of the static reaction system, employing pepsin and pancreatin in sequential application to the substrate was pursued. Optimized reaction conditions which negate the effect of product-induced competitive inhibition and maximize the enzymatic digestion of substrate were determined. Free amino acids liberated by the enzyme system were identified and quantified by conventional ion exchange chromotography. Results obtained with the static, in vitro assay procedure, clearly demonstrate that proteins previously autoclaved in the presence of reducing sugars were digested less completely than nonheated proteins. The technique appears to be a viable method for assaying the nutritive quality of proteins and will be evaluated against bioassay methods.